Status: 02.10.2023, 08:53 a.m.
Wind turbines in Saxony-Anhalt: The further the expansion progresses, the more important the question of recycling becomes. © Wolfram Weber/Imago
More wind power is the goal, not only in Germany. But when the turbines are getting on in years, their rotor blades are difficult to recycle.
Almost 30,000 wind turbines were turning in Germany in 2022. They generate 25.9 percent of Germany's electricity and are expected to make an even greater contribution in the future as part of the energy transition. However, the more plants are added and the older the existing ones become, the more the question of recycling comes into focus. "At present, the quantities that have to be dismantled are still so small that we are actually still ahead of the really big wave and have time to further develop technical solutions," says Steffen Czichon, head of the rotor blades department at the Fraunhofer Institute for Wind Energy Systems. On the other hand, the Federal Environment Agency expects almost 20,400 tonnes of waste to be generated by rotor blades alone over the next 000 years.
When it comes to recycling wind turbines, the foundation and tower are the smaller problem. They are mainly made of steel and concrete, for which there are established recycling processes. The rotor blades, on the other hand, which are often 50 or 60 meters long and can weigh more than 20 tons, consist not only of wood, metal and adhesive, but also of fiber-reinforced plastics. In older models, this is usually glass-fibre reinforced, in newer carbon fibre amplifiers it is plastic – and in both cases the individual components are difficult to separate from each other. Researchers and companies are therefore working to find solutions.
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Wind turbines profitable longer than expected
Until last year, the Bremen-based company Neowa recycled rotor blades made of glass-fibre reinforced plastic (GRP) by means of co-processing. In this process, the material is shredded and processed into granules that are used as a substitute fuel in the cement industry. At the same time, the glass content replaces part of the sand used in cement production.
But last year, operations were discontinued, says managing director Mika Lange, because the number of rotor blades had fallen sharply. The reason: Some of the wind turbines will be operated longer than the planned 20 years, as they are technically in order; thanks to the increase in energy prices, they will still be profitable even if the state subsidy expires after 20 years. Other sites are still waiting for approval to replace the old wind turbines with larger and more powerful turbines and are not yet dismantling them.
Further use as decking
At some point, however, these rotor blades will also have to be recycled. The Danish company Continuum is therefore currently planning to build several recycling factories. There, the rotor blades are to be shredded in order to be able to use them to produce composite material for kitchen worktops or panels for the construction industry. According to the company, the finished panels are made of 92 percent recycled material.
In addition, the process has the advantage that it should drastically reduce the CO₂ emissions generated by the currently used combustion and processing of rotor blade residues in cement factories. How exactly, Continuum does not want to explain. The first factory is scheduled for completion at the beginning of 2024, and five are planned throughout Europe, one of them in Germany. The factories will be powered by electricity from renewable sources and will each process around 36,000 tonnes of GRP per year.
The company Novotech in Aschersleben in Saxony-Anhalt also recycles GRP waste by means of mechanical recycling: The blades are shredded into a coarse powder, which is formed with wood chips and other additives at 170 degrees to form decking boards, which are made up to 30 percent from a rotor blade.
Closing recycling chains
In order to simplify recycling in the future, it is important to plan the final steps in the design process of the product and to design rotor blades in such a way that their starting materials can be separated more easily than before. Siemens Gamesa, for example, has developed the "RecyclableBlade", which uses a new resin whose chemical structure enables the separation of the different components. With a mild acid solution, resin, glass fibers and wood can be separated from each other and then reused in the construction industry, for consumer goods or in the automotive industry.
The German start-up Voodin Blades, together with a Finnish wood-based materials producer, is developing lighter rotor blades made of laminated veneer lumber. They are currently testing a 20-meter blade, with an 80-meter rotor blade planned next.
No circular economy at the moment
However, current recycling approaches do not yet lead to a true circular economy. So far, the materials have been reused, but the resulting product is usually of inferior quality – a classic downcycling. Research is still underway on how the existing concepts can be improved so that higher material values are achieved and energy consumption is reduced.
And politicians are also called upon. After all, a RecyclableBlade is far from being a "blade that will be recycled," says Steffen Czichon of the Fraunhofer Institute. "I always compare it to coffee cups. It's nice if they're compostable. But if I burn them, it doesn't help. And it's the same with recyclable rotor blades."
That is why it is very important to work on a closed recycling chain, for example by setting up central collection points for old rotor blades. However, this would require even clearer political framework conditions – and these have been lacking so far. But the expansion of wind energy is higher on the list of priorities than recycling. (Sarah Kröger)